The present invention relates to a photopatterning process for controlling the two dimensional spatial distribution of molecules in thiolate self-assembled monolayers ("SAMS"), particularly alkylthiolate self-assembled monolayers, on gold, silver and other substrates.
Precise control of the spatial position of the thiol compound molecules on a surface would permit manipulation of the chemical and physical properties of selected areas of the surface to bind inorganic, organic, and biological molecules and species. The ability to bind biological species such as proteins, enzymes, DNA and cells at known locations on surfaces could be important for a variety of technologies including biosensing, immunoassay diagnostics, DNA probe diagnostics and sequencing, pharmacological and toxicological testing, and cell growth studies. For example, in the area of biosensing, the ability to pattern and immobilize multiple proteins on surfaces would allow the construction of miniaturized, multi-analyte sensors capable of operating in blood vessels or on a single cell. In the area of DNA sequencing, the ability to immobilize DNA probes on surfaces with .ltoreq.10 micrometer spacing would be a key step in the fabrication of a new generation of miniaturized DNA sequencers supported on micro-chips. The same monolayer patterning process could also be used to lithographically pattern the underlying substrate (gold and silver) through the use of chemical etching reactions to form individually addressable micro-electrodes that would be useful for many chemical sensing and diagnostic applications.
Two processes are currently known for patterning alkylthiol monolayers on compatible substrates. The first is a mechanical method such as disclosed by N. L. Abbott, J. P. Folkers, and G. M. Whitesides in Science 257 (1992) at pp. 1380-1382, whereby portions of the SAM are physically removed by impressing a scalpel or carbon fibers across or on the SAM sample. This method suffers from the disadvantages, however, that the use of physical force may deform and damage the sample and/or the expensive pattern mask. The second process is a photolithographic method disclosed in Frisbie et al., Journal of Vacuum Science and Technology A, Vol. 11, pp. 2368-72 (1993). This process requires that a specific photo-active functional group (an aryl azide) be incorporated in the alkylthiol molecules, and thus is not generally applicable to other alkylthiols.